The present invention relates to a consumable polishing element for finishing optical glass.
Thus, optical glass is subjected to several trans-formation steps to arrive at the desired geometrical form and the final transparency.
The surfacing of optical glass, on the concave or convex surface, comprises at least three major steps:
rough grinding which gives the overall profile,
fine grinding which smooths the surface, and
polishing which further refines the surface and gives the glass its transparency.
Given the diversity of the profiles of optical glass, there have been provided specific supports, called xe2x80x9cpadsxe2x80x9d which are removably mounted on rigid rotating supports, called xe2x80x9ctoolsxe2x80x9d and which are used as consumable items to carry out operations of fine grinding and polishing.
These pads are generally fixed by an adhesive interface directly on the tool, or else driven by a material of very high coefficient of friction, itself fixed to an adhesive interface on the tool.
The glass is at present, for the most part, organic glass and the problems which arise are not necessarily in the technology of production of the shapes but rather in production times so as, on the one hand, to produce the required production within the shortest delay possible, and on the other hand, to decrease the cost.
It is accordingly necessary to find arrangements of material constituting the pads, which will permit gains in polishing time, which use less costly materials because they are consumable elements, which can adapt to the conditions of fine grinding.
There is known from French patent application 2.595.606 a multi-layer abrasive disc having two populations of calibrated abrasive grains. Thus, the disc comprises two layers, an internal one near the support, and the other one external and opposite the support. In the external layer, there are included grains of a size greater than those of the grains disposed in the internal layer, and this in a ratio of about 1.5 to give an order of magnitude.
It is thus possible to rough grind in a first phase and then to refine with smaller grains, under a water spray.
Preferably, such arrangements use abrasive grains included in a polymeric support of the type hardenable under ultraviolet light.
It is known that in such an embodiment, there are abrasive grains which are maintained in a polymeric support.
There exists another technique which consists in using pads in the form of discs of fibrous material which are sprayed, during the working period, with liquids including abrasive particles. These discs must have particular shapes so as to match as closely as possible the shape of the tool, and so as best to retain the liquid which lubricates and carries the abrasive particles, whilst limiting the wear of said fibers which could lead to deterioration of the quality of polishing and/or pollution of the bath.
The present invention relates to a consumable polishing element of the pad type which is economical, which permits great saving of time, which permits achieving a suitable polishing quality, which can be mass-produced, which can receive liquids with suspension of abrasives of known type, with a lifetime compatible with the parameters of polishing and which is simple to use.
To this end, according to the invention, the finishing polishing element for mineral or organic optical glass, adapted to be mounted on a rotating support, of a form suitable to that of the glass to be polished, comprising a base constituted by a polymeric film, a woven or non-woven fabric, is characterized in that it comprises at its surface a flocking comprising fibers of viscose and/or polyamide fixed on said base by means of a cement, said fibers having a length comprising between 0.3 mm and 1.0 mm, more particularly 0.5 mm.
As to the diameter of the fibers, it is comprised between 5 xcexcm and 25 xcexcm and preferably between 15 xcexcm and 25 xcexcm.
The base and the retained cement also have specific characteristics for optimum results.